The install.sh simply examines the local system's platform and architecture and uses that information to compose a URL of the directory in the S3 bucket for the full stack packages for supported platforms.

This installation includes everything above libc for the platform, including Ruby (1.9.2+), RubyGems and other assorted libraries and tools. This means you can still install Ruby in your preferred manner (by using a cookbook, of course) for your Ruby-based applications (if any) without modifying the Ruby environment that Chef needs, and you will have a Ruby version known and well tested to work with Chef.

The other installation paths (RubyGems, etc) continue to be available, but this is by far the least hassle, and will be the best supported method to install Chef on any platform Opscode supports.

Also, as of now, and version 0.10.10+, the chef-full bootstrap template will be the default for those who use knife bootstrap to automatically set up Chef client systems.

Note As of this writing, the full stack installer is in "beta". It will remain in this status until release, which will coincide with the Chef 0.10.10 version's release. It says on the install page that it is not supported, but will be soon.